Study On The Vibration And Noise Reduction Characteristics Of Damped Rail

With the rapid development of high-speed railway in China and the continuous improvement of train speed,the problem of wheel rail noise is particularly prominent.A large number of simulations and experiments results show that radiated noise generated by the rail vibration in the wheel-rail noise within 3000 Hz is dominant.And noise is proportional to vibration between the frequency 200 Hz and 2500 Hz.Therefore,it is meaningful to study the vibration law of the rail and put forward the corresponding measures for reducing the vibration and improving riding comfort.In the paper,a three dimensional model of constrained damped rail and vibration absorber rail is established by the finite element method/boundary element method to investigate the vibration and acoustic characteristics of the above measures.A knocking test was initially carried out for a single mass block of vibration absorber.Through theoretical and experimental analysis,the following conclusions can be drawn:(1)Modal analysis of standard rail shows that the rail web vibration is the largest at main frequency.Elastic damping layers and constrained layers are laid on the rail web.Modal analysis,harmonic response analysis,dynamic analysis and acoustic radiation analysis is carried out on the standard rail,the monolayer constrained damped rail and the multiple constrained damping rail.The results of harmonic response analysis show that increasing the thickness of the damping layer can increase the energy dissipation capacity of the constrained damping thickness.The damping and noise reduction capability of the damped rail increases with the increase of the damping material energy dissipation factor.The dynamic characteristics indicate that the constrained damping can reduce the peak displacements of the rail at significant frequencies effectively,and the rail damping effect of multiple constrained damping is the best.The acoustic vibration characteristics analysis results show that the monolayer constrained damping rail can reduce the noise by about 2.3d B,while the multiple constrained damping rail can reduce the noise by about 5d B.(2)The harmonic response analysis results of the vibration absorber rail show that the vibration amplitudes of the mass blocks increase sharply at the natural frequencies 420Hz?1410Hz and 1770 Hz while the vibration amplitudes of rail tread and rail web are greatly reduced.The dynamic characteristics indicate that the vibration absorber structure can reduce the vertical displacements at both rail tread and rail web effectively.The calculation and analysis of the acoustic radiation characteristics of the rail show that with moving speed of the moving load increasing,the vibration absorber can reduce the acoustic radiation power of the rail up to about 5.3d B,and with the increase of moving speed,the noise reduction slows down.(3)The knock test is performed on single vibration absorber mass to investigate the influence on the vibration characteristics of the glue or bolt connection method,the size of damping blocks and the quality of the masses blocks under the lateral excitation and the vertical excitation.The results show that in the middle and low frequency,the effect of vibration and noise reduction of glue connection is inferior to bolt connection,but in the high frequency,glue connection is better.The thicker damping block in the vibration absorber,the better the vibration and noise reduction,and the greater mass of the middle piece in the vibration absorber,the better the damping effect.